Plot

Whosemoralsarelastix, the chief of a neighboring Gaulish village, is a mean and greedy man who often does business with the Romans. When the Romans instigate new taxes, Whosemoralsarelastix asks the people of Asterix's village to safeguard a cauldron full of money, his village's treasures.

Asterix is left in charge of the cauldron full of sestertii which promptly gets stolen during the night. As the strict laws of the Gauls demand, Asterix is banished until he can make up for what he has done, and Obelix immediately “banishes” himself to stay with his friend. In order to regain his honor, Asterix, with Obelix's help, must find money to refill the cauldron and repay Whosemoralsarelastix.

Asterix and Obelix engage in many futile attempts to earn back the money. This includes trashing the pirates in the belief that they stole the money (although the pirates were for once trying to engage in an honest profession by turning their ship into a restaurant), selling boars (only to sell them at a ridiculously low price), prize fighting (only to win worthless statuettes), acting (Obelix insults the audience and ruins the company), gambling (only to lose their money when the tip doesn't pay off) and even trying to rob a bank (which is empty of money due to the recent tax increases by the Romans).

With little else to gain or lose they take the cauldron back to Whosemoralsarelastix's village. As they approach the village's area, they stumble upon and rob a Roman tax collector at the last minute. They beat up his escort and Asterix steals the money the taxman has obtained. But as they set off to take the money to Whosemoralsarelastix, Asterix catches a suspicious smell on the coins. The cauldron had previously been used for cooking onion soup — and the coins, fresh from the collector's coffers, smell of onion soup as well.

Asterix and Obelix go to Whosemoralsarelastix's village, which lies on a high cliff at the coast. Asterix confronts Whosemoralsarelastix with the onion soup-smelling money having correctly guessed that Whosemoralsarelastix stole back his own money and paid his taxes to the Romans to retain their favor, knowing that Asterix would go to any lengths necessary to get the money back and make up for his debt. A fight between Obelix and the villagers — although Obelix fails to fully understand why they are fighting — and Asterix versus the treacherous chief ensues. Asterix and Whosemoralsarelastix duel with their swords due to Asterix having exhausted his potion, but Whosemoralsarelastix is the better swordsman. Just as he is about to strike Asterix down, however, a section of the cliff suddenly gives way, the cauldron of money falling towards the sea while Whosemoralsarelastix barely manages to hold on to the side. Asterix rescues the treacherous chief and he and Obelix return to their own village while Whosemoralsarelastix cries his heart out over the lose of his money.

The money itself, however, falls right into the ship and the lap of the pirates, who for once conclude an adventure on a happy note for themselves. Back at Asterix's village a celebration is held for the return of the two heroes and the recovery of their honour, though Obelix, still a little confused over matters, asks why the cauldron was used to make onion soup at all.

Trivia

When Obelix suggests they get paid by telling people their adventures, Asterix rejects the idea as unlikely to raise any money. The joke is that, by this time, the series had made Goscinny and Uderzo two very wealthy men.

Goscinny and Uderzo themselves appear in the story. When the Roman dignitaries assemble at the theatre at the beginning of the show, Uderzo is shown talking to the Prefect, while Goscinny, on the right, amuses his neighbours with jokes.

The tax collector in the book appears to be a caricature of Valéry Giscard d'Estaing, the French minister of finance at that time. He later became President.

This is the first — and so far only — volume in which the pirates actually enjoy a happy ending. This is also the first of the few rare stories where their ship is not sunk (though they have already taken a beating earlier in this episode).

Nevertheless, the arc of the story is Whosemoralsarelastx's plot. And it's only by Asterix's intelligence that the plot is finally unravelled — while Obelix cannot understand what Whosemoralsarelastx'S double-cross was all about.

The fight at the end of the story is one of the rare times Asterix is seen using his sword, although he always carries it with him.